This is not to hard. but you need to be careful while messing with your game files. this also works for oblivion, and fallout 3, and new vegas. all of these games use the same engine.Ok enough of me saying jibber jabber and more guides i will be supplying images

First step. Download a mod from a site, today i will install: http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=8898 Ruby weapons so download that file now.

Second step is to locate your data Files head to your C_Drive then head to "Program Files/Bethesda Softworks/Morrowind/Datafiles you will now be cluttered with alot of files.

Third step is to unzip ruby weapons(Or any mod you download)

Open meshes and drag contents of that to the meshes folder in the datafile folder

Open textures and drag contents of that to the textures folder in the datafile folder

Open icons and drag contents of that to the icons folder in the datafile folder

Then Rename ruby weapons.esp to "RW.esp" so you spare 4 seconds of your life and add it to the datafile folder

Now go back to the "Morrowind" folder and open the morrwind.ini

Find "[Game Files]" and if you have both expansion pack's for morrowind